I think my orientation went for 3 or 4 hours but there were a lot of videos and maybe a 5 minute "here's the store and let's peek into the backroom" tour. You'll also get your training schedule since for the first week or two you won't be on the main one.
First day's probably going to be you getting paired with somebody (not necessarily the team trainer) and shown how to read labels, break out vehicles, push, etc.
Make sure to ask questions and pay attention because some of this stuff isn't hard, its just kind of tricky to explain. Like the labels.
Also for your first day I'd suggest being well hydrated, remember to ask about box cutters (took me 3 hours to figure out that one) and please move quickly. Don't need to run, but if you're lagging 6+ aisles behind your trainer while he's lugging a full pallet behind him, something's not right.
Not that I had to deal with that a couple weeks ago while training or anything like that.